Sufficient contrast differences between tissues in acquired images of patients and small animals are important for medical diagnosis and biomedical research. To increase the signal intensity difference between tissues in such acquired images contrast agents specific for that imaging modality are often used. A comparison between a single post-contrast agent administrated image with a single pre-contrast agent image, as selected by the operator, can be made to identify specific tissue volumes that have undergone contrast enhancement. Identification of which tissues undergo contrast enhancement, and how much enhancement, is an important indicator for many biomedical research and diagnostic applications. For in vivo imaging, however, respiration, cardiac, and non-specific motion of patients and small animals causes post-contrast injection images to be dissimilar when compared to a pre-single injection image making the comparison difficult.